I found a recipe that states to use around 1/2 tsp of vinegar for 1 quart of milk(0.5% vinegar to milk by weight) and another recipe that says 1/2 cup of vinegar for 3L of milk(3.7% vinegar to milk). That is around 7 times more vinegar. I want to make cottage cheese with the least amount of "vinegary" taste as possible, so how much vinegar do I need to use to effectively curdle the milk and produce cottage cheese. I am using distilled malt vinegar (which has a stronger taste than white vinegar) which I don't like, but that is the only available one in the UK.
Don't use vinegar at all. Use citric acid, which you should be able to get from a brewing or cheesemaking store, or get it online.
Not only does it have a "cleaner" flavor than vinegar, it also allows you to control the pH of the solution more precisely. A given quantity of citric acid diluted in distilled water always has the exact same acidity, which is not true of vinegar.
If you really can't get citric acid, lemon juice is going to have a less pronounced flavor than malt vinegar.
In terms of using the least acid necessary, that's an interactive process of adding a little acid, then watching what happens. Per Modern Farmer:
Many cheese recipes call for a specific amount of curdling agent – the juice of one large lemon, a quarter cup of vinegar, or one teaspoon of citric acid per gallon of milk is typical for farmer’s cheese – but the exact amount needed varies considerably based on the unique properties of each batch of milk (especially with non-homogenized, farm-fresh milk). It’s advantageous to use the least amount of acid possible to avoid an excessively tangy flavor. As soon as the curds form, stop adding the curdling agent.
I'll also add it's beneficial to use the minimum quantity of acid in order to get the softest curd texture.
Malt vinegar really isn't going to work. It's going to add a lot of flavor to anything you make with it.
If you really can't find white vinegar for sale, there are several other options. I personally use citric acid powder, which is generally harder to find in the USA than white vinegar, but if you have a health food / natural food store near you, try that. I believe you can also use tartaric acid (cream of tartar) but I've never tried it.
If you're in a pinch, you can also use lemon juice or try the vinegar out of a jar / jars of pickled peppers; I've use it from pickled sliced pepperoncinis particularly.
In any case, if you're not sure of the pH of what you're using, you may need to try a couple of times to get it right.